What I do on my own time is none of my employer's business. Mileage and regulations may vary, of course. I work about 20hrs a week on various side-gigs. Pretty strict about the working hours and work not overlapping with whatever my current employer is doing. It's nice to keep things separate.
That's usually fine, but if you worked for me doing what my team does and you were to be constantly tired out because of your side gig, you'd end up on a path to unemployment unless you committed to the full time job. Obviously, that only applies if you do actually turn up tired all the time. If you can pull off the longer hours, rock on!
But the problem is no full time job is secure. So every one is on his own. We are forced to create additional security through suffering additional hours. Can you suggest any way around it, without working additional hours and becoming financially independent.